Don't see an update option in Help. If there's a new update available, the app will tell you when the file opens each time unless you disable that option.
Once you download the updater you run it like you would any windows installer.
Please note that the latest update for FileMaker 12 was only for Mac and only really needed for those users upgrading to Mavericks in most cases.
I have a "Check for Updates" under the help menu option, running Filemaker 12 on Windows 7. It's about the 8th option down.
Yep. Missed it as I usually spot the update announcement here before the FileMaker app notifies me that one has been released...